Could this be an MMDC problem?

[FIRE UP]

Gents,
I've searched and read many issues regarding the old "VDC" units and the newer MMDC units. I'm thinking I may have developed an MMDC issue. Here's the scenario. We're presently on vacation and all has been going well. We were just outside of Lordsburg NM when all of a sudden, the speedo started dropping. I had the cruise set to 60. The speedo started dropping, stumbled a bit, then fell to zero.
The rig was corresponding to that too. In other words, the cruise had been shut down. Along with that, the tach went to zero, the oil pressure, water temp, turbo boost, and voltage gauges, all died. I think the air pressure gauges for both front and rear are still operative but, I can't remember. Another problem, and a serious one, the exhaust brake QUIT!

And, on my annunciator panel has "ABS" lit up, and "Check info center" is also lit up. When I look at the Medallion Info Center, it's reading "No data from Trans ECM and NO DATA from Engine ECM for 25 seconds", and is flashing that over and over.

Now, with all this going on, here's the deal. The engine is still running like a top. The trans is still shifting and operating flawlessly. All the lights, turn signals, brake lights and most other normal electrical stuff is still working just fine. And, I also have what's known as the "Trip-Tek" computer on board too. And, to those of you that don't know what that is, or don't have it, it's a system by which additional information, engine stats, trip odometer(s), maintenance items and more, are displayed on the monitor of the back up camera.

Well, since I lost all important gauges, I hit the Trip-Tek and all the engine stats, oil pressure, engine temp, trans temp, etc. are still just fine and operating just fine. My fuel gauge is working just fine.

Well, I pulled off the road, into town, and got lunch. Then we pulled the rig onto a side street and I called Freightliner help. They started to direct me to the MMDC 10-pin plug. They say those pins can get damaged due to the weight of the harness(s) in that area that tugging away at the plug. My phone was acting up too so I was in an out of the conversation with the Freightliner tech so, I thanked him for his time and went out and pulled that 10 pin plug and looked at it.

It looked just fine to me. Now, I also talked with my son, who works as an RV tech in San Diego and he has replaced many MMDCs due to faulty soldering on and in the pc board inside them. That's the same issues the older VDC units were having. What's up with these boys that do these boards? Anyway, to those who've had issues with the later MMDC units, did you have the same or close to the same symptoms? Is there a way to tell if the MMDC is actually bad without taking a chance on $400 or $500 worth of experimenting?

As stated, my speedo quit and so did my odometer. Now, to me, that's kind borderline "illegal" isn't it? I mean, heck you could drive that thing for another 100K miles and then get it fixed and, sell it as a "lesser mileage" vehicle". But, that's beside the points here. I sure could use some help here.
Scott

[Hooligan]

This may help: http://www.rvtechlibrary.com/electro...mdc_owners.pdf

If you need the VDC info, it is in the files section here (IRV2) iRV2 Forums - Files - VDU/ VDC Repair

[J Walker]

I had an incident similar to yours last Thursday on my Freightliner XCS chassis. I have the older VDC but I don't believe it was the cause of the problem. My dash lights lighted up and a buzzer went off. The speedometer did not work but the engine ran fine. The dash gauges went off but a check engine light remained on. After I turned the engine off and restarted everything worked and the check engine light went off. I checked the stored code and it said that there was a loss of voltage to the timing clock in the ECM. I had a momentary disconnect to the ECM. I will monitor the situation and if necessary attempt to fix it. I would advise that you check for a code.

[FIRE UP]

Originally Posted by Hooligan

This may help: http://www.rvtechlibrary.com/electro...mdc_owners.pdf

If you need the VDC info, it is in the files section here (IRV2) iRV2 Forums - Files - VDU/ VDC Repair

Hooligan,
I sure thank you for your trying to help with the links here. But, ours is the new version of the VDC. It's the MMDC unit. Probably close in operations etc. but, it is the newer version and, as I'm learning, has to diagnosed in different manners than the VDC unit. Thanks again.
Scott

Originally Posted by J Walker

I had an incident similar to yours last Thursday on my Freightliner XCS chassis. I have the older VDC but I don't believe it was the cause of the problem. My dash lights lighted up and a buzzer went off. The speedometer did not work but the engine ran fine. The dash gauges went off but a check engine light remained on. After I turned the engine off and restarted everything worked and the check engine light went off. I checked the stored code and it said that there was a loss of voltage to the timing clock in the ECM. I had a momentary disconnect to the ECM. I will monitor the situation and if necessary attempt to fix it. I would advise that you check for a code.

J Walker,
I thank you also for your insight here. Our "Check engine" light never came on when this all happened. This was not an engine operation problem. It's a communication problem with the J1939 data link and the newer version of your computer, the MMDC. These newer days autos/trucks/RVs/Motorcycles/space ships/submarines/etc. are way more complicated in terms of electronic controls, operational characteristics/diagnostics than yester year stuff, it's even funny. I still retain SOME diagnostic capability but, I don't even understand some of the wordage they're using now days.

So, at present, it's been diagnosed in a local Freightliner service center here in El Paso TX, that a FIFTY CENT resistor, that's located inside the $400.00 MMDC, has gone bad. So, they're air freighting one in from Memphis and we'll know maybe around 2:00 this afternoon if that was the culprit of our troubles. So, again, thanks for your input. Very much appreciate it.

[ernieh]

On the VDC (System 3) chassis there are 3 relays (solonoids) on the frame rail near the starter. One of those relays controls power to the "things up front" and can cause many strange things to happen (perfectly running engine with crazy indications is one of them). I'm not sure if the MMDC is powered the same way, but if you have 3 relays back there one of them could certainly be your problem.

BTW, one of the 3 is the starter solonoid. Can't remember what the other one is for.

[FIRE UP]

Originally Posted by ernieh

On the VDC (System 3) chassis there are 3 relays (solonoids) on the frame rail near the starter. One of those relays controls power to the "things up front" and can cause many strange things to happen (perfectly running engine with crazy indications is one of them). I'm not sure if the MMDC is powered the same way, but if you have 3 relays back there one of them could certainly be your problem.

BTW, one of the 3 is the starter solonoid. Can't remember what the other one is for.

Hey ernieh,
Thanks for your attempt as assisting me in this might dilemma. I'm kind of in between a rock and a hard place here. You see, I'm about 700 miles from home, plus or minus a hundred. And, I'm on southern route which is kind of what I "Must" follow. The reason I must is, I have no exhaust brake. If I run a northern route, it takes over, up and down a ton of grades. And trying to stop this AMTRAK train without an exhaust brake is a bit hard on things.

The reason I'm telling you all this is because, I just spent, three of the most horrible days of my travels, in one of the most rot gut towns(El Paso TX), at one of the most hideous service centers I've ever had to deal with(On the Border Freightliner), in an absolute horrible camp/RV spot (Mission RV Resort)(two miles from the Freightliner center) and, I wasted $450.00 paying them to diagnose my problem(s) and they came up with "0" and it cost me that much!!!! They wanted me to stay so they could do more analyzing. NOPE! I told them we're OUT OF HERE!

So, I'm going to attempt to make that 700 mile run, without gauges, speedo, tach, exhaust brake, cruise control etc. because I'm not in favor of paying another Freightliner service center to "fish" around, at a rate of about $130.00 an hour, trying to find a loose connection or, a bad ground etc. when once I get this beast home, I can take as long as I need to tear into the wiring, at suspected places and try and find stuff for myself.

I'm told that the VDC system is considerably different than the MMDC system. I have no real proof of this as I'm learning about my own. What's really hard is trying to find, someone who's knowledgeable about it and can talk down to my level to teach me at least the basics and how things work. And, possibly might suggest places to start looking for the problem.

You see, even though the gauges are dead, every once in a while, I hit a sharp bump on the freeway and at that precise moment, the speedo and the tach, jump to life, but just for a second or less. That leads me to think the problem is just a bad connection or ground. But, where????

That Freightliner Service center in El Paso ordered up and installed a new MMDC and it did not fix the issue. They almost tried to make me pay for it at a cost of $400.00, and it didn't fix the issue. Well, you can guess what I told them.

So, this is one of the worst predicaments we've ever been in while traveling. But, one good thing here. The engine and trans are both operating just fine. And, I have the trip-tek system to assist me in monitoring the engine vitals. I have the Magellan 1700 Road mate to tell me my speed. So, as long as I try and keep it on as flat and level ground so I don't overtax my brakes, I think I'll be fine.

Normally I don't frown too bad on electrical problems but this one is a dusy. Not only does it involve the MMDC but, there's a big, or little brother to the operation too. And that's something I just learned about. It's called the J1939 Data Link. The powers to be all think that's the main issue here. Both my engine and trans ECMs are not talking with the Medallion Information Center and that's just part of the issue. My ABS light is on too. It's all part of the same problem.
Scott

[ernieh]

Fireup, If you can take a quick look for those solonoids, it might be worth your while. You don't have to replace at this time. Just jumper the right one or even connect both cables to the same terminal and you will have power "up front".

You can never hurt anything by trying the jumper and it might just help you to get home with something besides a blank screen. The starter solonoid will be obvious so you only have 2 choices to see if your gauges come back. Mine were very hard to see from the bottom but fairly easy to access from the top.

That "sharp bump effect" certainly could be a solonoid.

Good luck.

[FIRE UP]

Originally Posted by ernieh

Fireup, If you can take a quick look for those solonoids, it might be worth your while. You don't have to replace at this time. Just jumper the right one or even connect both cables to the same terminal and you will have power "up front".

You can never hurt anything by trying the jumper and it might just help you to get home with something besides a blank screen. The starter solonoid will be obvious so you only have 2 choices to see if your gauges come back. Mine were very hard to see from the bottom but fairly easy to access from the top.

That "sharp bump effect" certainly could be a solonoid.

Good luck.

ernieh,
Well Sir, so far, I've found no solenoids on the frame anywhere near the starter. I'm pretty sure they're not there. Even though the techs at the Freightliner Service Center in El Paso are incompetent in my opinion, their conclusion, as well as Freightliner Customer Assistance at the 1-800 number, was that the "J1939" Databus link, is "Open". Based on all the info I've consumed in learning about the MMDC, the J1939 and, the diagnosis procedures, test results and more, it's definitely looking like a problem with that J1939 Databus or, as Freightliner calls it, the "Data Link".
They, as usual, don't make it easy to trace wires and find plugs/connections etc. The cab diagnostic port was hidden beyond belief. They, "Freightliner" had it mounted to the inside firewall, about two inches off the carpet, facing down. How in the world is a tech supposed to get to that port? Anyway, I removed it and did the suggested tests. They came out the same as the rear diagnostic port. So, someplace, along that 36' motor home, that data link is disconnected or broke.
Scott

[FIRE UP]

Well Gang,
It's all better now. Due to the help from my son who's an RV tech here in San Diego, we determined the area where the problem was with the J1939 Data link. It would have taken me years to find it using a "one man" method and, it would be shear luck at that. Even an experienced tech would have taken a seriously long time. What we did was, I was in the drivers seat with the engine running and, my son was underneath cruising around on a creeper, touching and tweaking various plugs, connectors etc. for that data link.
Well, after about 5-10 minutes, my gauges "popped". That is to say, the came to life for a brief second or two. We were on those little FRS radios so I yelled at him and told him he was very close to the problem area. He narrowed it down to a certain plug/connector. It was late and he had to go.

So, the next morning, I went out and dove into a more in depth analysis. As usual, this problem was not easy to get at. In fact it was in a bundle of looms, all tightly wired tied together, straight above the air dryer. What a serious pain.

So, I cut a few ties and then pulled the plug/connector down as much as I could so I could attempt to work on it and narrow it down to an exact spot of broken wires. I laid there for an hour, with a VOM clamped to the bottom side of the frame, some long wires attached to it, and the other end of them were attached to the diagnostic port in the front of the cab.

I kept seeing 120 ohms in the wire in question. Once in a while, it would drop to the called for spec of 60 ohms. I could get it to stay but, as soon as I let go of the tweaked position of the connector/wires, it would go back to 120 ohms. I tried and tried to narrow it down to a broken wire or, bad contact in the pins, inside the connector. The connectors used, as you'll see in the picture are Deutsch type DT-04 and are a triangle, three wire connector. There are pins and sockets inside. A push button lever allows the connector to be separated.

I only had one wire that was the problem. As stated, there's three wires, and, if you look on any of your wiring diagrams for engine/chassis wiring, you see a YELLOW, for J1939 Positive, a GREEN for J1939 negative, and a BLACK for the J1939 "Shield". Well, the shield does nothing in terms of transporting data so, there was no need to test it. The YELLOW one, I tested for continuity and it was good from the start of the tests so, that was ruled out.

Now, the GREEN, it was the problem. No continuity for the full length of the coach. So, back to the original part of this post. Since the problem area was found, but not narrowed down to the pin point spot, it was coming down simply replacing the connector/plug. I knew it was very, very close to it or, in it. So, I started trying to disassemble that plug and all of a sudden, SNAP! I broke part of it. CRAP, now I've done it. So, I called my son and asked him, since I broke the original Deutsch connector and don't have any means to repair it or any part of it, would it be OK to use a "Weather Pack connector??

He said absolutely fine. While maybe not "quite" as good as a Deutsch, the Weather Pack is a quality connector and, seals just as well, from all entry points. So, I figured what the heck, since it's already broke, I finish breaking it and see what's inside. Well, that was a rewarding maneuver. What I found and you'll see in the picture(s) is, the YELLOW and BLACK wires, where attached and crimped to the pins, are perfect but, the GREEN, is broken off, right at the pin.

Now, here's the deal. While it might be thought that the "stress" of the wires caused this, in my "long term experience", that's not possible. The reason, those wires are in a seriously tight, sealed, insulation, and, they're also in a strong, black corrugated plastic loom and, they're supported on both sides of the plug/connector to other looms and wire tied beyond belief. So the movement of just "ONE" of those wires enough to break it off at the pin, IMPOSSIBLE.

So, again in my experience, what happened was, the original installer of that particular plug/connector used the wrong groove on the wire strippers and basically "cut" the majority of the strands while prepping it for the pin to be crimped on there. So, the remaining few strands (not known how many) lasted 49K miles before it finally gave way due to the finite vibrations. So, that was a huge relief off my mind. Now, to repair the situation. All I had was the tools and equipment to repair with a Weather Pack type connector.

I figured wire is wire. As long as a good job of repairing and sealing the joint, as good as factory, it would work. So, in the pics, you'll see the repair.

In the end, I hope this never happens to any of you. While the break in this particular wire did cause some alarm, the engine and trans were not effected. And, as stated way earlier, I have the "Trip-Tek" system installed in the coach so, I was able to monitor engine vitals in the return trip home. I had lost two critical components to driving the coach, the Exhaust brake and Cruise control. My route home was carefully chosen to encounter the least need for the exhaust brake.

The drive home, around 1000 miles, was a pain to NOT HAVE CRUISE CONTROL!!! I want to thank any of you that tried to assist me in this problem/issue. While many thought it was a "LOSS OF POWER" in the system/wiring, I was convinced it was simply a bad connection in a connector or, a broken wire, not a power loss. It could mean the same thing but, it was not a loss of power.

In the end I sure learned a lot about my coach, the electrical systems, the "J1939 Data Link", the "J1587 Data Link" , their individual functions and how they effect your coach.

As a side note, even our local Freightliner electrical Tech who I talked with face to face and showed him schematics of the wiring of the coach, was stumped a bit. At first he stated that I "DIDN'T HAVE A J1939" system, I only had a J1587 system. I proved him wrong. He then studied the drawings/schematics and still thought it was a loss of power problem. I simply told him what I've learned and how I thought the system worked and, what I've seen in my own test results.

Ok, enough babbling, take a look at the pics, see what you think. Again, I hope it never happens to any of you.
Scott

[Grimesy]

Good job, Freightliner charged me over $700.00 to locate a $12.00 part that created the same problem. Whatever happened to pride of workmanship ?

Don G.
Santa Clara,CA

[Sammie]

Scott,
I'm happy that you were able to diagnose and fix your wiring problem knowing that if anyone could find it, you would be the one. I've been following your posts for two weeks now with hopes that this would not ruin your vacation although being stuck in El Paso for one day would ruin anyones vacation. I stayed there one night several years ago on my way to Carlsbad Caverns and swore I would never return to that crappy city.

On two of my previous gas coaches I had some electrical chassis issues that luckily were resolved on the road and only cost me a day or two of down time. So I know that they can cause quite a bit of frustration.

Anyhow, I'm glad you made it home safe and sound and can hopefully make new plans for a more pleasent vacation.

Sammie

[FIRE UP]

Originally Posted by Grimesy

Good job, Freightliner charged me over $700.00 to locate a $12.00 part that created the same problem. Whatever happened to pride of workmanship ?

Don G.
Santa Clara,CA

Don G.
Thanks for the comment. While an immediate thought could be a "what happened to pride of workmanship", I'm almost inclined to give the tech that did the wiring or, at least that part of it, the benefit of the doubt. In the time that we've owned this rig, I've had two semi-major electrical issues. One was the loss of a ground that feeds the MMDC and that caused my total annunciator panel to malfunction which included both my air gauges as well. A call to Freightliner Customer Assistance helped me cure that one in about 15-20 minutes on the phone.
The second electrical issue was this one that I just repaired. Now, to take over 49,000 miles and three owners, to manifest itself, I'd say is simply just the luck of the draw. Yes, that particular wire, in that particular connector, I THINK, was done incorrectly but, most likely he, or she, never realized the mistake and thought all was well. That is of course if, that really was the cause of that issue. We'll never know.

Originally Posted by Sammie

Scott,
I'm happy that you were able to diagnose and fix your wiring problem knowing that if anyone could find it, you would be the one. I've been following your posts for two weeks now with hopes that this would not ruin your vacation although being stuck in El Paso for one day would ruin anyones vacation. I stayed there one night several years ago on my way to Carlsbad Caverns and swore I would never return to that crappy city.

On two of my previous gas coaches I had some electrical chassis issues that luckily were resolved on the road and only cost me a day or two of down time. So I know that they can cause quite a bit of frustration.

Anyhow, I'm glad you made it home safe and sound and can hopefully make new plans for a more pleasent vacation.

Sammie

Sammie,
Thanks to you too for the nice comments. Just about when I think I'm over my head in either approaching a repair or, even thinking about one on this beast, something compels me to take the dive, and jump right in with both feet. Each time I actually do something right, it sure as heck makes me feel good knowing that, 1, I learned more about this beast, 2, I "again" saved some money in doing a repair myself and, 3, I can post it here and maybe, just maybe it might help someone down the line. I've said before, while these things, (all new autos, trucks, motorcycles, motor homes and more) are way better than yesteryear models, they are by far SERIOUSLY more complicated and, while they can and many do last for years before presenting a break or need a repair, when they do break, it's BIG!

I really, really want to thank Freightliner Customer Assistance for being there in situations like this. How many of us can call Ford, GM, Chrysler, Honda, and many other manufacturers, NINE YEARS AFTER THE BUILD DATE and, be the THIRD OWNERS with no warranty, and get right to a person who tries their darndest to satisfy and help remedy a problem a customer/owner is having with one of their products? And will send drawings, schematics and the like all in an effort to please and help a total stranger.

While there are folks out there that down play Freightliner in their search for a new coach, I'd use another Freightliner in a heartbeat. Thanks again for all who've helped here. Yes, Sammie, El Paso's definitely not on our "need to visit again" list.
Scott

[Hooligan]

Thanks for the update. Glad YOU fixed it. Keep grinning..

[cbeierl]

Great job, Scott! Glad to see that you finally tracked that down.